Chromosomes, Cell Division, Meiosis and Chromosome Flashcards
Function of Centromere
Hold sister chromatids together
Telomeres
Termini of chromosomes
Function of Telomeres
Protect chromosome against DNA damage as DNA repair enzymes are able to recognise blunt ends of chromosome
How are Okazaki fragments produced
The lagging strand is synthesised discontinuously
What is used to join Okazaki fragments
DNA ligase
What initiates the assembly of Okazaki fragments
RNA primer
End Replication Problem
when the last piece of RNA primer at the 3’ end is removed, the DNA cannot be extended and leaves a gap
How is End Replication Problem Solved
Telomerase is used and adds the telomeric sequence to lay out new DNA
DNA can only synthesise in which direction
5’ to 3’
Do most somatic cells express telomerase
No
Do germ cells express express telomerase
Yes
Product of Mitosis
2 cells with identical DNA
Stages of Mitosis
Prophase
Metaphase
Anaphase
Telophase
Prophase
Chromosome becomes visible
Metaphase
Spindles fully formed and chromosomes align in the centre
Anaphase
Linkage between sister chromatid is broken
Telophase
Nuclear membrane is reformed
Where do spindle fibres attach to on the centromere during mitosi
Kinetochore
Features of Chromatin
Packed with positively charged histones
Compacted into nucleosomes
Core of 8 molecules of histones
Solenoid structure
Central structure in which the heterochromatin get assembled to and is 30nm in diameter
Heterochromatin
Tightly packed and inactive
Eurochromatin
Loosely packed and active
Purpose of packaging DNA
Histones (positive) neutralise DNA (negative)
Takes up less space
Inactive DNA folded into accessible region
Karyotyping uses what type of stain
Giemsa
